Cap-polymer

Polymer is separated from the polymerisation slurry and slurried with acetic anhydride and sodium acetate catalyst. Acetylation of polymer end groups is carried out in a series of stirred tank reactors at temperatures up to 140°C. End-capped polymer is separated by filtration and washed at least twice, once with acetone and then with water. Polymer is made ready for extmsion compounding and other finishing steps by drying in a steam-tube drier. 

Traces of formaldehyde, present in neat end-capped polymer or produced by processing polymer under abusive conditions, detract from polymer stabihty. Commercial resins typically contain formaldehyde scavengers. Nitrogen compounds, especially amines and amides, epoxies, and polyhydroxy compounds, are particularly efficacious scavengers. 

The reduction of transition metal salts in solution is the most widely practiced method for synthesis of metal colloidal suspensions [7]. In the preparation process, polymer is often used in order to prevent the agglomeration of metal particles as well as to control their size. Ahmadi et al. [5] reported that the concentration of the capping polymer affects the shape of platinum particles obtained by salt reduction. This means that the addition of a... 

A very efficient energy transfer (producing emission at 613 nm) was observed in PL spectra of the perylene end-capped polymer 361 in solid films. This material had the highest QE (>60%) among the fluorene- perylene polymers, although the performance of its PLED has not yet been reported [434],... 

Gouanve F, Schuster T, Allard E, Meallet-Renault R, Larpent C (2007) Fluorescence quenching upon binding of copper ions in dye-doped and ligand-capped polymer nanoparticles a simple way to probe the dye accessibility in nano-sized templates. Adv Funct Mater 17 2746-2756... 

More recently, the Diels Alder cycloaddition was used as a single-step strategy for attaching diene-capped polymers onto CNTs sidewalls through grafting to methods (see Section 3.3.1.6 for more details). Examples include attachment of furfuryl-functionalized polystyrene [35] and cyclopentadienyl-functionalized polymethyl methacrylate [36]. 

Macroinitiators for ATRP can be produced from polymers obtained from non-ATRP polymerization by appropriate conversion of their end groups. For example, hydroxyl-capped polymers obtained by cationic or anionic chain polymerization or even step polymerization can be esterihed with 2-bromopropanoyl bromide to yield Br-capped polymers that are ATRP macroinitiators. 

The facile addition of primary and secondary amines to Cjq has been used to synthesize polymer-bound Cjq [126-133]. Solutions of precursor polymers containing primary amino groups in the side chain or secondary amino groups in the main chain [132] were allowed to react with CgQ in a "buckybalT fishing process. Fullerene end capped polymers (type V) are accessible by reaction of amino-terminated polystyrene [128], poly(ethylene glycol) or poly(propylene glycol) [129] with Cgo. 

It is apparent from these data that all of the polymers, including butadiene, exhibit an association as dimers, and that there is no reason to expect any higher states of association for polyisoprene or polybutadiene. This is confirmed not only by the viscosity data on the active vs. terminated "capped" polymers, but also by the fact that there was no significant increase in viscosity when the polystyryl lithium was "capped" by butadiene or isoprene, i.e., all three types of chain ends are associated in the same way, as dimers. 

The triphenyl methyl or trityl radical behaves as a radical trap and favors the polymerization-termination which is thermoreversible and thus allows the insertion of a new polymeric sequence. In 1982, Otsu et al. [49,213,214] proposed an interesting example involving phenylazotriphenylmethane as Initer (initiator-terminator) able to initiate a free radical polymerization from the phenyl radical. Alternatively, the trityl end-capped polymer can be utilized as an original macroiniter for the polymerization of a second monomer and yields block copolymers as follows ... 

A mixture consisting of poly(s-caprolactone-co-trimethylene carbonate) (0.129 mmol), the Step 3 product (1.79 mmol), pyridine (0.62 mmol), and 20.5 ml of CH2CI2 were stirred overnight at ambient temperature. The end-capped polymer was precipitated in diethyl ether and then purified by fractionation using DMF and diethyl ether/methanol, 8 2 the product was isolated in 86% yield. 

Alkyl halides are widely used as cocatalysts in combination with aluminum alkyl halides or aluminum halide Lewis acids. Tlie reaction scheme in Fig. 9-2 illustrates the complicated equilibria which may affect the initiation process. Each carbenium ion can initiate polymerization or remove an ethyl group from the counterion to produce a saturated hydrocarbon, REt, and a new more acidic Lewis acid. The propagating macrocarbenium ions can also terminate by the same process to produce ethyl-capped polymers and new Lewis acids. Thus, even though the initiator is ostensibly dielhylaluminum chloride there may be major contributions to the polymerization from ethyl aluminum dichloride or aluminum chloride. 

Recently, it has been found that the elimination of the hydroxylamine from a nitroxide-capped polymer occurs particularly facilely upon the controlled monoaddition of maleic anhydride and maleimide derivatives under the creation of a very useful functional end group, that is, the often detrimental side reactions can also be put to good use.115... 

After freeze-drying the end-capped PSa branch, the excess silane was removed under high vacuum by heating the resulting porous material at 50 °C for at least 3 days. After the silane was removed the end-capped polymer was dissolved in benzene, which was introduced directly by distillation from the vacuum line. 

On the other hand, Scherf and coworkers used N,N-bis(4-methylphenyl)-N-phenylamine as the end-capper to yield the polymer 16 (end-capper concentration 3 mol%) its single-layer device (ITO/PEDOT PSS/16/Ca/Al) exhibited maximum luminance of 1600cdm 2 and efficiency of 1.1 cdA-1, with CIE coordinates (0.15, 0.08) at 8.5 V [29]. This efficiency is higher than that of non-end-capped polymer 3 (that is, bromine exists at each chain end) by one order of magnitude and was attributed to an efficient hole trapping at the... 

Further support for the proposed mechanism is provided by the results of experiments involving phenylbromide instead of ethylbromide (Jj6). The polarizable TT electrons of this aryl compound allow it to effectively compete with styrene for the sites on the lithium surface and thus the Wurtz coupling reaction becomes dominant. Similar results were obtained with ethyltosylate. Although the reaction of tosylate with living polystyrene is rapid and quantitative, yielding ethyl capped polymers, its reaction with the monomer and metallic lithium produces only 10% of the ethyl capped polymers, the remainder being evolved as butane. Again, the aromatic nature of tosylate allows it to compete with styrene for the lithium sites. 

Ethylene oxide (EO) can also be polymerized via ROP. Huang et al. used potassium 2-dimethylaminoethoxide as the initiator for the polymerization, followed by quenching with methanol. The dimethylamino-capped polymer was exposed to 365-nm light in the presence of benzophenone and capped with HTEMPO to form the initiator (Scheme 39) [291]. 

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